1. Field of the Invention
The present invention relates in general to oil-industry mechanical engineering and more particularly, to multistage oil-well pumps for pumping out formation fluid.
2. The Prior Art
Known in the art are enclosed-design peripheral (vortex) pumps for transferring liquids free from abrasive particles, said pumps comprising an impeller appearing as a disk provided with cells arranged along its periphery, a peripheral-lateral working duct, an intake and a discharge branch pipe. The inlet and pressure chambers of the pump working duct are separated from each other by a web along the impeller periphery (cf. the textbook xe2x80x9cNovel low-delivery high-head pumpsxe2x80x9d by K. N. Spassky and V. V. Shaumian. Moscow Mashinostroyeniye PH, 1973, p. 122 (in Russian)).
A disadvantage inherent in such pumps resides in an abrupt reduction of their pressure head and efficiency in case of increased end and radial clearances when transferring liquids containing abrasive particles.
Known in the art is also a combination pump (cf. Swiss Patent #544,890, IPC F04 D 5/00, 1973), comprising an enclosed impeller and vortex bladed rings arranged along the disk periphery and having radial dimensions exceeding the radial dimension of the impeller, an annular impeller outlet, and an annular webbed chamber of the vortex wheel.
A disadvantage inherent in such pumps resides in complicated construction of their working members, especially in manufacture of a multistage submersible pump, as well as an abrupt pressure head and efficiency reduction in the case of increased end and radial clearances in the vortex portion of the pump construction when transferring liquids containing abrasive particles.
Known in the art is a multistage centrifugal submersible pump for pumping out formation fluid from oil wells. Stages of such a pump comprise an enclosed impeller ar a guide vane assembly having vanes which are extendable beyond the diametrical dimension of the outside lid of the guide vane assembly. The impeller of the pump stag has specially shaped vanes interposed between the driving and driven disks (cf the textbook xe2x80x9cCentrifugal submersible pumps for oil productionxe2x80x9d by N. A. Bogdanov. Moscow Nedra PH, 1968, pp.38-50 (in Russian).
Among the disadvantages of such a pump stage are low pressure developed by the stage at low stream rates and unstable performance characteristics when handling two- or three-phase oil-water-gas media.
Therefore the present invention has for its primary and essential object to provic such a stage of a mulstistage submersible pump that is capable of increasing the pressur head at low delivery rates and of higher stability of performance characteristic when handling two- or three-phase oil-water-gas media.
Said technical result is attainable with the stage of a multistage submersible pump, having an impeller which comprises a driving disk and a driven disk with vanes interposed therebetween, and a guide vane assembly with shaped vanes whose leading edges extend beyond the outside diameter of the external lid of the guide vane assembly. The stage according to the invention has triangular cells provided at the periphery of the impeller driving disk on the lateral surface thereof said cells being open towards the disk outer side, and a side annular channel on the surface of the external lid of the guide vane assembly, said surface mating with the impeller.
The herein-proposed pump stage is also characterized in that the surface of the lateral annular channel of the guide vane assembly is spaced apart from the upper edge the impeller cells at least 0.3 the depth of the latter.
Another distinguishing feature of the proposed pump stage resides in the fact that the radial length of the cells is not in excess of 0.3 times the driving disk radius.